The present invention is directed to an arrangement for optical fiber measuring devices. More specifically, the present invention is directed to an arrangement for optical fiber measuring devices wherein a sensing device is optically coupled to a transmitter and to a receiver through respective optical fiber bundles.
Optical fiber measuring devices offer distinct advantages over other types of measuring systems. Unlike electrical measuring systems, for instance, optical fiber measuring devices are insensitive to electromagnetic irradiation. Additionally, optical fiber measuring devices permit measurements to be made free of electrical potential and dissipation heat. Optical fiber measuring devices are thus particularly well-suited to medical technology applications, such as measuring a patient's pulse and respiration in the high-frequency field of a nuclear spin tomograph.
German Provisional Patent 38 33 131 discloses a photoelectric pulse recorder having an optical fiber sensing element that is optically coupled to a transmitter and a receiver by an optical fiber bundle housed in an optical fiber cable. This fiber bundle is integrally cast at one of its ends in the sensing element, such that a cross-section of the fiber bundle terminates at the application surface of the sensing element, with the longitudinal axis of the fiber bundle perpendicular to the application surface. The other end of the fiber bundle is firmly coupled to a plug connector, in which the transmitter and the receiver are also arranged. In the plug connector, the fiber bundle fans out into a transmitting bundle and a receiving bundle, leading to the transmitter and the receiver, respectively. The plug connector is electrically connected to an operating unit.
In known optical fiber measuring devices such as the pulse recorder described above, the sensing element is undetachably connected to the transmitter and the receiver; however, in many applications a detachable connection is desirable. For example, when measuring the pulse of a patient in a nuclear spin tomograph, it would be beneficial to have a detachable plug-in connector between a fiber bundle leading to a sensing element affixed to the patient and two optical fiber bundles installed in a support, namely a transmitting bundle and a receiving bundle. A requirement for any such configuration is that light transported by the transmitting bundle and reflected off the break at the connection must not be received by the receiving bundle; otherwise, light from the optical transmitter will create an interfering offset at the optical receiver. A further requirement for any such configuration is that the plug-in connector be easy to manufacture and maintain.